Two-speed hydraulic pumps



D 1963 H. a. CHLEBOWSKI 3,112,705

TWOQSPEED HYDRAULIC PUMPS Filed 001.. 5, 1961 a g i 5 3 1 W Z 1 3 5 W lj .A 4 w j wfiwwgwwj WJ/I3 INVENTOK 17 [5 HARRY B. CHL .e-Bowsm Unitedstates Patent 3,112,705 TWG-SiEED HYDRAULKI EUMFS Harry Chiehewski, St.Paul, Minn, nssigncr of onethird to .lane Waller], Pvliiwaul: e, Wis.,one-third to Betty Laliier, Sc'otia, N.Y., and one-third to Marjorie(Ihlehowshi, St. Paul, Minn.

Filed Get. 5, 1951, Ser. No. 143,2fi1 5 Claims. (6!. l03--37) Thisinvention relates to an improvement in two-speed hydraulic pumps anddeals particularly with a simple and effective apparatus for pumping agreater or lesser hydraulic force to operate this member.

In a typical form of my apparatus, the apparatus includes a combinedhigh and low pressure piston which is designed to force hydraulic fluidfrom a suitable source of supply to a member to be operated upon, suchas a movable piston. When the movable piston is operated against a lightpressure, the low pressure piston functions to move the driven piston ata relatively high rate of speed. However, as the resistance to movementof the driven piston increases, the low pressure piston ceases tofunction and hydraulic pressure is forced by a relatively high pressurepiston pump, to drive the driven piston at a lower rate of speed.

A feature of the present invention resides in the provision of a pistonpump which includes a relatively large diameter piston pump which ismovable in a cylinder to draw the fluid from a suitable reservoir and todirect it against the member to be moved. The low pressure pump isprovided with an axial recess therethrough which accommodates arelatively smaller diameter pump piston. A spring means is interposedbetween the two pump pistons so that both pistons are normally operatedin unison. However, when the pressure against which the pumps are worhngexceeds the spring pressure, the large diameter low pressure pump ceasesto operate and the reciprocation of the high pressure pump pistoncreates the necessary pressure to accomplish the desired result.

it is an object of the present invention to provide a piston, diaphragm,or other suitable means which is engage-able with the peripheral surfaceof the low pressure piston and which is frictionally engaged with thelow pressure piston by the pressure of the pump. When the pressure beingpumped by the pump exceeds a predetermined amount, this member will beforced against the low pressure piston with suiiicient force to hold thelow pressure piston from movement during reciprocation of the inner highpressure piston.

These and other objects and novel features of the resent invention willbe more clearly and fully set forth n the following specification andclaims.

in the drawings forming a part of the specification:

FE l a section view through a two-speed hydraulic pump, showingdiagrammatically the arrangement of parts in one position thereof.

FlGURE 2 is a view similar to FIGURE 1 showing the high pressure portionof the pump in operation.

In view of the simplicity of the present apparatus, the pump is showndiagrammatically. The pump is shown in conjunction with a work pistonand cylinder to which the hydraulic fluid under pressure is delivered.Obviously, the member being actuated may vary. Furthermore, the deviceis shown in conjunction with a piston which operates in one directiononly under pressure. As is obvious, means could be provided forcontrolling the how of fluid from the pump to selectively drive thedriven member in either direction.

As illustrated, the pump includes apump body it having a pump cylinder1'1 and a driven piston cylinder '12. The cylinder 12 can be consideredto comprise a ram ice chamber designed to slidably support a ram :13.The mm 13 is moved in an upward direction as viewed in the figures whenfluid under pressure is directed to the ram chamber 12. The pump body idis provided with an inlet passage 14 which communicates with a source offluid supply such as a reservoir or the like. A check valve 15 isprovided in the inlet passage 14 to permit the fluid to be drawn intothe pump cylinder 11 but to prevent the return flow of fluid to thereservoir. A passage -16 connects the lower end of the pump cylinder 11to the ram chamber 12, and a check valve v17 controls the fio-w of fluidthrough the passage 16, the check valve 17 permitting a flow of fluidfrom the pump chamber 11 to the ram chamber 12, but preventing a reverseflow. The check valves 15 and 17 are normally provided with the usualbiasing springs to hold them ciosed when not being forced open, thesprings being omitted to simplify the showing.

A low pressure iston -19 is slidably supported in the pump cylinder 11and includes a relatively large diameter stem 2-5 which extends from thecylinder at one end thereof. The piston l? is provided with a suitableseal such as 211 to seal the piston with respect to the wall of thecylinder. The piston 19 and its stem 26 are provided with an axial bore22 which is designed to accommodate a high pressure piston 23. Suit-ablesealing means such as 2.4 are provided between the piston 23 and thebore 22 so as to form a seal therebetween. The high pressure piston 23includes an operating stem 25 which is reciprocated in a verticaldirection by any suit-able means, not illustrated in the drawings. Aspring 26 is interposed between the upper end of the stem 26 and ashoulder 27 on the operating rod 25 and the reciprocating movement ofthe rod 25 is normally transmitted through the spring to the piston stem2%? so that the piston 119 will reci rocate in unison with the rod 25.

A cylinder 29 is provided in the body :19, the axis of which preferablyintersects the axis of the cylinder iii. A pressure plug St is slidablysupported in the cylinder 29, and is sealed from the Walls thereof by asuitable sealing means 31. A passage 32 provides commtuu'cation betweethe connecting passage 16 and the cylinder 2?. As a result, the interiorof the cylinder 29 and the end of the pressure plug '36, is at all timesequal to the pressure in the ram chamber 12 or approximately equalthereto.

In the operation of the apparatus, the operating rod 25 is reciprocatedby any suitable means, to cause a similar reciprocation of the highpressure piston 26. The downward force on the rod 25 is normallycommunioated through the spring 26 to the top of the piston stem 29,thus causing movement of the piston 19 in unison with the high pressurepiston 23. As a result, the hydraulic fluid is pumped at a relativelyhigh rate of volume from the reservoir into the ram cylinder to move theram cylinder upwardly. When the pressurewithin the cylinder i l exceedsthe force of the spring 26, the high speed pump 23 moves downwardlyindependently of the low speed pump 20. At the same time, the pressunewithin the cylinder 11 and ram chamber '12 increases so that the forcewithin the connected cylinder 29 causes sufiicient pressure against thepressure plug it? to hold the stem :25 of the piston 19 from motion. inother words, the build-up of pressure within the pump cylinder servesnot only to increase the force tending to compress the spring 26, butalso increases the friction caused by the plug 38 against the pistonstem 20. As a result, the pressure plug will lock the low pressurepiston in position, and permit the independent reciprocation of the highpressure pump 23. As a result, the ram 13 will be moved with greaterforce and at in relatively slower sneed.

While in the description, mention is made of the vertical movement ofthe pistons and the ram, it should be understood that this descriptionis only in relation to the particular showing and in ref rcnce to theparticular drawings, as the pistons may move in any desired direction.1? urthermore, while means is shown for moving the ram 13 in onedirection, means could be provided for moving the ram in oppositedirections, and suitable means, such as the relief valve 35 could beprovided for permitting the ram to return to its original position.

The piston 19 may be stopped at any point in the stroke of the piston'In this case, the piston 19 will remain stationary until the pressure incylinder 11 is great enough to overcome the friction of plug 3% on thestems 2A of piston 19 and the pressure of spring 26. When this pressureis attained, piston 19 will move (gradually or rapidly depending on thepressure in cylinder 11) toward the end of the cylinder that is oppositethe intake valve and Will continue to move until the piston 19 engagesthe upper end of the pump body 19. Thus the piston 19 will graduallyretract to the upper end of the cylinder even if the high pressurepiston 23 is operated with a stroke of reduced length.

As indicated, the piston 19 may be positively moved in an upwarddirection with the piston 23 by any suitable means, such as by a head ora shoulder on the lower end of piston 23. In the drawings, a snap ringas is provided in a groove 37 at the lower end of piston 23 forming theshoulder in question. When the pistons do not move in unison, the piston19 is held at the top of its stroke.

In accordance with the patent statutes, I have described the principlesof construction and operation of my improvement in two-speed hydraulicpumps, and while I have endeavored to set forth the best embodimentthereof, I desire tohave it understood that changes may be made withinthe scope of the following claims Without departing from the spirit ofmy invention.

I claim:

1. A two speed hydraulic pump, the pump including a pump body includinga pump cylinder, a low pressure piston slidably supported in saidcylinder, said pump body including an inlet to and an outlet from, oneend of said cylinder, said :body including a pressure chamber in thewall of said cylinder, said chamber having an end communicating withsaid pump cylinder, a friction member in constant engagement with saidpiston and movably supported in said chamber for movement toward andaway from said piston, passage means connecting said outlet to saidfluid actuated member and to the other end of said chamber, a checkvalve in said inlet preventing a reverse flow of fluid from saidcylinder, a second check valve means in said outlet prevent a reversehow of fluid through said passage means, said low pressure piston havingan axial passage the-rethrough, a high pressure piston slidablysupported in said axial passage, spring means interposed between saidpistons for transmitting movement of said high pressure piston towardsaid one cylinder end to said low pressure piston, said friction memberbeing operable upon an increase in pressure in said passage means toengage against said low pressure piston to resist movement thereof.

2. The structure of claim 1 and in which said low pressure pistonincludes a stem portion extending from the other end of said pumpcylinder and against which said friction member engages.

3. The structure of claim 1 and in which said friction member includes aplug slidably supported in said chamher.

4. A two-speed hydraulic pump including a pump body including a pumpcylinder, a low pressure piston slidably supported in said pumpcylinder, an axial aperture through said low pressure piston, a highpressure piston slidable through said axial aperture, 2. springinterposed between portions of said low pressure piston and said highpressure piston through which force is transmitted to urge said lowpressure piston toward said one end of said pump cylinder, an inletpassage to said one end of said pump cylinder, a check valve in saidinlet passage to prevent a reverse flow from said pump cylinder to saidinlet passage, an outlet passage from said one end of said pumpcylinder, a second check valve in said outlet passage controlling thereverse flow of fluid to said pump cylinder, a second cylinder in thewall of said pump cylinder having its axis intersecting the pumpcylinder axis, a pressure plug member is said second cylinder andfrictionally engageable at all times against said low pressure piston,and a -by-pass leading from said outlet to said second cylinder tocommunicate fiuid pressure to said plug member and to urge said pressureplug member toward said low pressure piston.

5. The structure of claim 4 and in which said low pressure pistonincludes a piston stern extending from the other end of said pumpcylinder, said pressure plug member being engageable against said pistonstem.

References Cited in the file of this patent UNITED STATES PATENTS1,829,451 McNab Got. 27, 1931 2,083,854 McGee June 15, 1937 2,495,151Vickers Ian. 17, 1950 2,545,685 Cook Mar. 20, 1951 2,854,061 RomitoSept. 30, 1958 2,895,454 Tebb et a1. luly 21, 1959 2,954,740 Wilkenlohet al. Oct. 4, 1960 FOREIGN PATENTS 122,408 Australia NOV. 25, 1944141,635 Australia June 18, 1951

1. A TWO SPEED HYDRAULIC PUMP, THE PUMP INCLUDING A PUMP BODY INCLUDINGA PUMP CYLINDER, A LOW PRESSURE PISTON SLIDABLY SUPPORTED IN SAIDCYLINDER, SAID PUMP BODY INCLUDING AN INLET TO AND AN OUTLET FROM, ONEEND OF SAID CYLINDER, SAID BODY INCLUDING A PRESSURE CHAMBER IN THE WALLOF SAID CYLINDER, SAID CHAMBER HAVING AN END COMMUNICATING WITH SAIDPUMP CYLINDER, A FRICTION MEMBER IN CONSTANT ENGAGEMENT WITH SAID PISTONAND MOVABLY SUPPORTED IN SAID CHAMBER FOR MOVEMENT TOWARD AND AWAY FROMSAID PISTON, PASSAGE MEANS CONNECTING SAID OUTLET TO SAID FLUID ACTUATEDMEMBER AND TO THE OTHER END OF SAID CHAMBER, A CHECK VALVE IN SAID INLETPREVENTING A REVERSE FLOW OF FLUID FROM SAID CYLINDER, A SECOND CHECKVALVE MEANS IN SAID OUTLET PREVENT A REVERSE FLOW OF FLUID THROUGH SAIDPASSAGE MEANS, SAID LOW PRESSURE PISTON HAVING AN AXIAL PASSAGETHERETHROUGH, A HIGH PRESSURE PISTON SLIDABLY SUPPORTED IN SAID AXIALPASSAGE, SPRING MEANS INTERPOSED BETWEEN SAID PISTONS FOR TRANSMITTINGMOVEMENT OF SAID HIGH PRESSURE PISTON TOWARD SAID ONE CYLINDER END TOSAID LOW PRESSURE PISTON, SAID FRICTION MEMBER BEING OPERABLE UPON ANINCREASE IN PRESSURE IN SAID PASSAGE MEANS TO ENGAGE AGAINST SAID LOWPRESSURE PISTON TO RESIST MOVEMENT THEREOF.